The present invention relates generally to an image recording/playback apparatus which is designed for use in a system for monitoring various events taking place in a place concerned by making use of movie techniques. More particularly, the present invention is concerned with an improvement of the image recording/playback apparatus which makes it possible to survey and/or retrieve a monitoring picture or image recorded over an extended period within a short time on the order of one several-tenth of the recording period. Further, the present invention is concerned with a image recording/playback method and a recording medium which stores the method in the form of a program executable with a computer.
In a place such as supermarket, convenience store, elevator hall or the like which is frequented by a large number of persons and which is difficult to be surveyed by a person in charge of management or watching, a monitoring camera is installed for the purpose of preventing accidents and/or crimes in advance. In this conjunction, the monitoring system for monitoring the places such as mentioned above by viewing the moving images or pictures taken by such monitoring camera can generally be classified into two types, i.e., a system which necessitates a constant survey of collected images picked up by the monitoring cameras by a person at a center station (hereinafter referred to as the online-type monitoring system) and a system in which pictures or images taken by the monitoring camera are stored accumulatively for allowing survey and inspection thereof later as occasion requires, e.g. upon commitment of offense or crime (hereinafter this type of monitoring system will be referred to as a storage-type monitoring system). The storage-type monitoring system involves scarcely personnel expenses when compared with the online-type monitoring system. For this reason, the former is adopted widely in practical applications. At this juncture, it is noted that in the storage-type monitoring system, a time-lapse video recorder is primarily employed for storing and playback the pictures or images as picked up by the monitoring camera.
With the time-lapse video recorder, such a video recorder is meant which is modified on the basis of a conventional video recorder such that the time interval for recording the images at a rate of thirty frames per second is increased to an interval on the order of several frames per second for recording only sparsely. Thus, with the time-lapse video recorder based on the conventional video recorder, it is possible to perform the recording over a period of about 180 hours (about eight days) by recording at the rate of one frame per second by using a tape medium capable of recording over 120 minutes with the conventional video recorder. Of course, by increasing the frame interval, recording can be performed over a further extended period which will however be accompanied with dropout of image of some object under monitoring, to a disadvantage. For this reason, the recording interval which exceeds one second or so is not adopted in practical applications. Further, it is conceivable to use a tape medium which can ensure a recording duration which exceeds 120 minutes or so. However, in consideration of durability (or possibility of breakage) of the tape medium, the tape which allows recording over 120 minutes or so is usually employed. Such being the circumstances, the longest recording time duration of the time-lapse video recorder based on the conventional video recorder is approximately 180 hours.
Image recording is performed starting from the leading end of the tape toward the trailing end thereof. Upon reaching the trailing end of the tape in the image recording operation, tape rewinding operation is automatically put into effect, whereon overwriting operation is performed, starting again from the leading end of the tape. In this manner, a series of images can be stored ordinarily over a time span of 180 hours or so at maximum. For perusing or surveying the images as recorded, substantially same method as that for the conventional video recorder can be resorted to. However, when the images recorded by the time-lapse video recorder based on the video recorder are to be reproduced straightforwardly in a same manner as the picture recorded by the conventional video recorder, the playback speed may amount to be thirtyfold.
Accordingly, the time-lapse video recorder is ordinarily provided with a mechanism for allowing the recorded images to be reproduced at a rate of several frames per second.
Among the time-lapse video recorders, there has been developed such a recorder in which a digital recording on a hard disk is adopted. With the time-lapse video recorder which is based on the VHS video recorder, the recording head may be damaged because recording/stop operations are mechanically repeated. Besides, the tape medium is likely to become degraded, incurring deterioration of quality of the reproduced images. These problems can certainly be solved by the digital recorder mentioned above. Parenthetically, the digital recorder is generally termed the digital time-lapse video recorder distinctively from the time-lapse video recorder based on the conventional VHS video recorder.
As will now be appreciated from the foregoing, monitoring images can be stored over an extended time period with the time-lapse video recorder. However, the time-lapse video recorder suffers serious problems with regard to the image reproduction for the survey or perusal. Firstly, it has to be pointed out that several times as long as the recording time of the recording medium (120 minutes in the case of the video tape) will be taken for observing thoroughly all the images or pictures recorded during the extended period of for 180 hours. Secondly, effectiveness of search and/or perusing (or surveying) operations is extremely poor because of disordered states of the objects concerned with images of significance and insignificance being recorded concurrently and alternately. In the present state of the art, reproduction is performed simply from the leading end of the tape while observing the images only rumblingly, which will often result in failure to notice the image of interest or concern, to a great disadvantage.
As is apparent from the above, the perusal of the images recorded accumulatively with the time-lapse video recorder imposes a great burden on the user because of necessity for concentrative observation of the images over a much extended time period.
At this juncture, it should be added that as an approach for solving the problems mentioned above, there has already been proposed such a monitoring system in which an infrared sensor such as a man-sensor is combined with the time-lapse video recorder. However, such system suffers many drawbacks. Firstly, with the time-lapse video recorder based on the VHS video recorder, mechanical portion for effectuating the recording/stop operations will be damaged at a relatively high failure rate because of frequent on/off operations. Secondly, reliability can not be ensured in respect to the effective coverage range of the sensor and the sensitivity thereof. Thirdly, high cost will be involved in retrofitting the monitoring system. For these reasons, combination of the sensor with the time-lapse video recorder is seldom adopted in the practical applications, leaving the aforementioned problems unsolved.
The fundamental problem of the conventional time elapse video recorder can be found in that the image data as inputted to the recorder are simply recorded on a time serial basis without performing any classification of the data. In this conjunction, let""s suppose a case where a person monitors a certain place as to occurrence of some event. In that case, he or she will take notes of the events such as, for example, coming-in/out of persons, positional changes of equipment or the like for classification and orderly arrangement with a view to facilitating the search or retrieval of the events as recorded. Further, upon perusal or survey, only the images of concern (e.g. images showing features of incomers or intruders, destruction of equipment or facilities, theft of something valuable) will first be checked briefly and thereafter examined in detail without haste. Contrivance of this sort will become more important as the time taken for the monitoring increases.
It goes without saying that even in the monitoring system in which the time-lapse video recorder is employed as the image recording/playback apparatus, capability of orderly arrangement, classification and selection of the images which would be performed if the images are handled by a person, as mentioned above, can contribute considerably to reduction of the time taken for the search while alleviating significantly the burden imposed mentally on the user.
As will be understood from the foregoing, the conventional image recording/playback apparatus typified by the time-lapse video recorder suffers drawbacks in respect to the storage of images with classification and orderly arrangement and the surveying facility which allows the user to search the image of concern without any appreciable difficulty.
In the light of the state of the art described above, it is an object of the present invention to provide an image recording/playback apparatus for a monitoring system which apparatus can perform recording and reproduction of monitoring images very effectively and conveniently for the user.
More particularly, it is an object of the present invention to provide an image recording apparatus, a monitoring system and a monitoring method which can detect various events occurring in a place subjected to the monitoring and store the images with classification and orderly arrangement in dependence on the types or species of the events while presenting an interface capable of reducing significantly the time taken for the user to survey or peruse the images.
It is also an object of the present invention to provide a recording medium which stores the monitoring method in the form of a program or programs executable by a computer.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to an aspect of the present invention an image recording/playback apparatus for a monitoring system which apparatus includes a unit for inputting and digitizing images on a time-serial basis, an input image displaying unit for displaying the image being inputted currently, a monitored event detecting unit for detecting a monitored event from the image as inputted, an image recording decision unit for deciding whether the image as inputted is to be stored or not on the basis of the event as detected, an image storing unit for storing an image which is decided to be recorded by the image recording decision unit, a monitored event storing unit for recording a storage location of the image as stored and the monitored event information as detected, an image selecting/disposing unit for searching the event information which meets user""s perusal demand and selecting the images for perusal to thereby lay out the event(s) together with the information thereof, and a monitoring information display unit for displaying one or a plurality of the images and/or the event information as laid out.
As the recording medium for the image storing unit and the monitored event storing unit mentioned above, a hard disk, a DVD-RAM or a random access memory of flash-memory type may be employed.
Further, the monitored event detecting unit mentioned above may be implemented by resorting to a scheme which is disclosed, for example, in the U.S. Pat. No. 5,721,692 titled xe2x80x9cMOVING OBJECT DETECTING APPARATUSxe2x80x9d. According to this method, presence/absence of change of the background structure, presence/absence of change of illumination, presence/absence of a moving object and the like are detected, respectively, as monitored events on the basis of difference degree between the images inputted upon sampling and an image recorded in the past. Further, a region of flesh color is detected. Additionally, decision is made as to whether or not a face candidate area or field exists in the scene in which a moving object is found. On the basis of the results of the detection and the decision mentioned above, monitored event such as xe2x80x9cpresence of a person whose face is presented most closely to the monitoring cameraxe2x80x9d is detected.
In a preferred mode for carrying out the invention, the aforementioned image recording decision unit may be so designed as to decide whether or not the recording is to be performed in consideration of the latest monitored event, species/histories of the events already detected, difference between the time point at which the immediately preceding image was recorded and the current time point, residual capacities of the media employed in the various storage units, minimum time duration for storage as designated by the user.
Further, the monitored event storing means mentioned previously may preferably be so designed as to store characteristic quantities concerning the monitored event(s) such as the location where the image is to be stored in the image storing unit, date/time of occurrence and termination of the event, position of the event within the image frame, a camera identifier (or identifier of the place being monitored) in the case where decision is made that image recording is to be performed for the event(s).
In another preferred mode for carrying out the present invention, the image selecting/disposing unit may be so designed as to search or retrieve the monitored event information in accordance with the user""s survey request such as, for example, xe2x80x9ca list of detected face imagesxe2x80x9d, xe2x80x9ca list of events occurred within given one hourxe2x80x9d, xe2x80x9cdisplay in animation the images recorded for a given monitored eventxe2x80x9d, xe2x80x9ca list of changes of installations at a place being monitoredxe2x80x9d, xe2x80x9cdistribution of monitored events in one dayxe2x80x9d and the like, to thereby generate a screen image for a display unit by selectively disposing the appropriate images in a manner easy for viewing by the user. Parenthetically, rules/algorithms concerning the objects for search or retrieval and the image/layouts for each of the screen images may previously be incorporated as firmware in the apparatus.
In yet another preferred mode for carrying out the present invention, there may be provided additionally a unit for establishing synchronism among a plurality of images being displayed or monitored event information in accordance with surveying operation performed by the user.
By virtue of the arrangement mentioned above, an interface which enables display of plural images in association with one another can be realized, whereby the monitored event information as well as the images can be presented to the user very efficiently and multilaterally.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings, being appreciated that many modifications and variations of the present invention are possible in the light of the techniques disclosed herein.